6.8-stable review patch. If anyone has any objections, please let me know.
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From: Matthew Wilcox (Oracle) willy@infradead.org
commit fd1a745ce03e37945674c14833870a9af0882e2d upstream.
Return 0 for pages which can't be mapped. This matches how page_mapped() works. It is more convenient for users to not have to filter out these pages.
Link: https://lkml.kernel.org/r/20240321142448.1645400-5-willy@infradead.org Fixes: 9c5ccf2db04b ("mm: remove HUGETLB_PAGE_DTOR") Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Reviewed-by: David Hildenbrand david@redhat.com Acked-by: Vlastimil Babka vbabka@suse.cz Cc: Miaohe Lin linmiaohe@huawei.com Cc: Muchun Song muchun.song@linux.dev Cc: Oscar Salvador osalvador@suse.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/proc/page.c | 7 ++----- include/linux/mm.h | 8 +++++--- include/linux/page-flags.h | 4 ++-- 3 files changed, 9 insertions(+), 10 deletions(-)
--- a/fs/proc/page.c +++ b/fs/proc/page.c @@ -67,7 +67,7 @@ static ssize_t kpagecount_read(struct fi */ ppage = pfn_to_online_page(pfn);
- if (!ppage || PageSlab(ppage) || page_has_type(ppage)) + if (!ppage) pcount = 0; else pcount = page_mapcount(ppage); @@ -124,11 +124,8 @@ u64 stable_page_flags(struct page *page)
/* * pseudo flags for the well known (anonymous) memory mapped pages - * - * Note that page->_mapcount is overloaded in SLAB, so the - * simple test in page_mapped() is not enough. */ - if (!PageSlab(page) && page_mapped(page)) + if (page_mapped(page)) u |= 1 << KPF_MMAP; if (PageAnon(page)) u |= 1 << KPF_ANON; --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1204,14 +1204,16 @@ static inline void page_mapcount_reset(s * a large folio, it includes the number of times this page is mapped * as part of that folio. * - * The result is undefined for pages which cannot be mapped into userspace. - * For example SLAB or special types of pages. See function page_has_type(). - * They use this field in struct page differently. + * Will report 0 for pages which cannot be mapped into userspace, eg + * slab, page tables and similar. */ static inline int page_mapcount(struct page *page) { int mapcount = atomic_read(&page->_mapcount) + 1;
+ /* Handle page_has_type() pages */ + if (mapcount < 0) + mapcount = 0; if (unlikely(PageCompound(page))) mapcount += folio_entire_mapcount(page_folio(page));
--- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -945,12 +945,12 @@ static inline bool is_page_hwpoison(stru * page_type may be used. Because it is initialised to -1, we invert the * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and * __ClearPageFoo *sets* the bit used for PageFoo. We reserve a few high and - * low bits so that an underflow or overflow of page_mapcount() won't be + * low bits so that an underflow or overflow of _mapcount won't be * mistaken for a page type value. */
#define PAGE_TYPE_BASE 0xf0000000 -/* Reserve 0x0000007f to catch underflows of page_mapcount */ +/* Reserve 0x0000007f to catch underflows of _mapcount */ #define PAGE_MAPCOUNT_RESERVE -128 #define PG_buddy 0x00000080 #define PG_offline 0x00000100